Gas flux chamber assemblies are used to measure trace gas emissions (e.g., CO2 and methane) from soils. One such assembly is the LI-8100 Long-Term Chamber by LI-COR Biosciences. The LI-8100 Long-Term Chamber is electrically actuated via a geared, motorized chain drive mechanism to move a chamber between two positions—one over the soil sampling area and another away from the soil sampling area. Trace gas emissions are measured when the chamber is over the soil sampling area. When measurements are not being taken, the chamber is moved away from the sampling area to expose the soil to the environment, thereby allowing environmental factors (e.g., wind, rain, sun, etc.) to reach the soil just as it would if the chamber were not present. This allows a researcher to measure soil CO2 flux in as representative an environment as possible, thereby ensuring maximum yield from the sample area.
The LI-8100 Long-Term Chamber uses a strut mechanism to move the chamber through a seven-inch radius vertical circular arc over and away from the sampling area. The strut mechanism maintains the chamber opening downward to avoid collection of precipitation and debris while in the open or moving state. The unique advantage of the LI-8100 Long-Term Chamber as compared to other chamber designs is the ability to move the chamber clear from the sampling area, which is important for long-term unattended measurements. An unobstructed sampling area allows natural exposure to sunlight, shading, precipitation, and temperature effects, thereby minimizing the influence of the testing equipment on the measured gas flux. In contrast, assemblies that simply move a chamber directly above the sampling area can shade the sampling area with the chamber, thereby creating an artificial condition that can influence the flux measurements. Also, in systems where the chamber is stationary and a movable chamber lid covers and uncovers the chamber, the chamber itself protrudes from the soil surface even when a measurement is not being taken and obstructs the sampling area.